In the present art, a manually tightened chuck generally comprises a chuck body member, jaw, nut, front sleeve and rear sleeve For example, authorized Chinese Patent CN 2440611 applied by the applicant discloses a manually tightened chuck, the chuck comprises a chuck body member, jaw, nut, front sleeve and rear sleeve. Three jaws are placed, respectively, in three inclined bores distributed uniformly on the chuck body member. Between the nut and the jaw a thread connection is adopted, the rear end of the nut provides a thrust bearing, the rear end of the thrust bearing is provided with a blocking ring, and on the rear end of the chuck body member the rear sleeve is assembled. The nut is of duplex-half structure. The duplex-half structure is combined into an integral through a steel sleeve, parallel planes are adopted for torque transmission between the front sleeve and the rear sleeve and between the front end of the front sleeve and the chuck body member there is provided a blocking sleeve. The disadvantages of the manually tightened chuck are: since the thrust bearing and blocking sleeve provided in the rear end of the thrust bearing are used to achieve relative rotational movement between the nut and chuck body member, its structure is more complicated, so as to increase the cost for machining and assembling.
The present invention provides an improved manually tightened chuck, particularly a manually tightened chuck mounted in machining equipment, for example, a drilling machine tool. An object of the invention is to overcome the disadvantages of present art mentioned above and provide an improved chuck, the structure providing for rotational movement between the nut and the chuck body member is more simple for reducing cost of machining and assembling.
According to a manually tightened chuck provided by the invention, the chuck comprises a hollow chuck body member, having three inclined bores along its periphery equally spaced and inclined forwardly toward a central axis of the chuck body member. In each inclined bore a jaw is installed slidably. On the outer peripheral surface of the chuck body member, a nut is sheathed, and is connected with each jaw through threads. The outer peripheral surface of the nut is provided with a front sleeve, and between the front sleeve and the nut there is provided structure for torque transmission. The outer peripheral surface of the chuck body member is provided with a rear sleeve and at the middle of the chuck body member a stepped part extends radially outwardly and includes a surface opposed to the rear end face of the nut. Circular grooves or rails are machined on the above-mentioned surface and/or on the rear end face of the nut for receiving a plurality of rolling bearing balls.
To compare the manually tightened chuck according to the invention with the prior art, the present invention has the following advantages: since rolling balls are placed directly between the nut and the chuck body member whereby both of them may rotate relatively, a blocking ring and rolling ball holder may be eliminated, not only to cause the integrated structure of the chuck to be more simple and compact, but also in the meantime to reduce the cost for machining and assembling.